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Ecological Applications, 21(3) Supplement, 2011, pp. S3–S17
2011 by the Ecological Society of America
Agricultural conservation practices and wetland ecosystem services
in the wetland-rich Piedmont-Coastal Plain region
1,3 2
DIANE DE STEVEN AND RICHARD LOWRANCE
1
USDAForest Service, Southern Research Station, Center for Bottomland Hardwoods Research, Stoneville, Mississippi 38776 USA
2USDA Agricultural Research Service, Southeast Watershed Research Unit, Tifton, Georgia 31793 USA
Abstract. In the eastern U.S. Coastal Plain and Piedmont region, diverse inland wetlands
(riverine, depressional, wet flats) have been impacted by or converted to agriculture. Farm Bill
conservation practices that restore or enhance wetlands can return their ecological functions
and services to the agricultural landscape. We review the extent of regional knowledge
regarding the effectiveness of these conservation practices. Riparian buffers and wetland
habitat management have been the most commonly applied wetland-related practices across
the region. Riparian Forest Buffers (RFB) have been most studied as a practice. Water quality
functions including pollutant removal, provision of aquatic habitat, and enhanced instream
chemical processing have been documented from either installed RFBs or natural riparian
forests; forest buffers also serve wildlife habitat functions that depend in part on buffer width
and connectivity. Wetland restoration/creation and habitat management practices have been
less studied on regional agricultural lands; however, research on mitigation wetlands suggests
that functional hydrology, vegetation, and faunal communities can be restored in depressional
wetlands, and the wetland habitat management practices represent techniques adapted from
those used successfully on wildlife refuges. Other conservation practices can also support
wetland services. Drainage management on converted wetland flats restores some water
storage functions, and viable wetlands can persist within grazed flats if livestock access and
grazing are managed appropriately. Because wetland hydrogeomorphic type influences
functions, ecosystem services from conservation wetlands will depend on the specifics of how
practices are implemented. In a region of diverse wetlands, evaluation of ecological benefits
could be improved with more information on the wetland types restored, created, and
managed.
Key words: Coastal Plain; conservation practices; ecosystem services; Piedmont; restoration; riparian
buffers; water quality; wetlands; wildlife.
INTRODUCTION agriculture by the early 20th century led to widespread
With a humid climate and topography favoring poorly land abandonment, natural forest regrowth, and active
drained soils, the U.S. region represented by the reforestation (Kauppi et al. 2006), even as wetland
Piedmont and Coastal Plain physiographic provinces drainage continued in some areas. Today, over 60% of
(Fig. 1) is a wetland-rich landscape. Despite a long the Piedmont and Coastal Plain east of the Mississippi
history of Native American occupation and impacts from River is forested, and only ;20% is in some form of
early European settlement, the region still has approxi- agriculture (USDA 2006). Over 70% of nonfederal
mately half of all freshwater wetlands and 95% of all regional wetlands are on lands classed as forest, while
estuarine wetlands (by area) in the conterminous United ,10% are on agricultural lands (USDA NRCS 2009).
States (Tiner 1987, Hefner et al. 1994, Moulton et al. Conservation practices implemented by the U.S.
1997). Colonial settlement of the eastern coasts was well Department of Agriculture (USDA) under Food
established by the early 1700s, and lowland wetlands were Security Act (Farm Bill) programs can improve the
drained to support farming and grazing. However, by the maintenance and delivery of wetland ecosystem services
early 1800s, trends in population growth and territorial on privately owned agricultural lands. However, the
expansion shifted agricultural development and major regions distinctive land use history has shaped current
wetland impacts to states west of the Appalachian interactions between agriculture and wetland conserva-
Mountains and to the Mississippi Valley (Dahl and tion practices. The Natural Resources Conservation
Allord 1996). In the east, eventual collapse of upland Service (NRCS) initiated the Conservation Effects
Assessment Project (CEAP) to develop methods for
quantifying environmental benefits derived from Farm
Manuscript received 9 February 2009; revised 14 August Bill programs and practices, and a major component is
2009; accepted 24 August 2009. Corresponding Editor: J. S.
Baron. For reprints of this Special Issue, see footnote 1, p. S1. assessing benefits to wetland services (see Eckles 2011).
3 E-mail: ddesteven@fs.fed.us This paper forms part of a multi-region information
S3
S4 DIANEDESTEVENANDRICHARDLOWRANCE Ecological Applications
Special Issue
FIG. 1. Subregions of the Gulf–Atlantic Coastal Plain states, USA. The thick solid line indicates the approximate northern
extent of Hammonds (1970) Gulf–Atlantic Division landform; dotted and dotted-dashed lines delineate the Piedmont, Rolling
Coastal Plain, and Coastal Flats; and the thick dashed line shows the Lower Mississippi Alluvial Valley (LMV) region.
Hammonds system is the basis for the USDA Land Resource Regions (LRR), where Piedmont plus Rolling Coastal Plain is the
Atlantic–Gulf Slope LRR, and the Coastal Flats equals the Atlantic–Gulf and Florida Lowlands LRRs.
synthesis to summarize current knowledge of the the Appalachian Highlands or within the region and
ecosystem services provided by wetland-related conser- discharge to Gulf–Atlantic coastal waters. Wetlands
vation practices and to identify knowledge gaps and comprise ;16% of regional land area, but subregional
emerging issues (Brinson and Eckles 2011). Our review percentages vary from low (,5%) to high (;30%) along
focuses on the eastern Piedmont–Coastal Plain, which the seaward gradient from the dissected Piedmont to the
spans the Atlantic and Gulf Coast states from New poorly drained Coastal Flats (Tiner 1987, Hefner et al.
Jersey to Mississippi (Fig. 1). We describe key features 1994). Wetland diversity is notable and contributes
of regional wetlands, summarize trends in land use and functional complexity to the landscape. All wetland
wetland change, and review the available research on the hydrogeomorphic classes (riverine, flat, depressional,
effectiveness of wetland-related practices on regional estuarine, slope, and lacustrine; Smith et al. 1995) occur
agricultural lands. The Lower Mississippi Alluvial in the region, but the first four predominate. The major
Valley (LMV) and its associated wetlands are reviewed inland freshwater classes (riverine, flat, depressional) are
separately (Faulkner et al. 2011); both the Florida embedded within uplands and thus are directly affected
Everglades region and the western Coastal Plain differ by agricultural activities. Apart from some localized salt
sufficiently in ecoregional and agricultural character that hay farming (see Philipp 2005), agricultural production
we will generally not include them in our treatment. affects estuarine (saltwater) wetlands mainly indirectly
through impacts on the quantity and quality of inland
PIEDMONT–COASTAL PLAIN WETLANDS:ECOLOGICAL waters reaching the coasts. Consequently, we focus our
FUNCTIONS AND SERVICES review on freshwater wetlands.
The Piedmont–Coastal Plain region (Fig. 1) is These regional wetlands have hydrologic, biogeo-
traversed by many river systems that originate either in chemical, and biotic functions that provide the ser-
April 2011 PIEDMONT–COASTALPLAINWETLANDSERVICES S5
vices to maintain sustainable ecosystems and provide somewhatwiththedegreeofsaturationandcontactwith
human benefits. All wetland types function in nutrient mineral soil. Water outflows export dissolved organic
cycling and transformations, the specifics of which carbon and organically bound nutrients, but are low in
depend upon the organisms present, the substrates, inorganic nutrients. Interactions among hydroperiod,
and system hydrology. Likewise, all wetland types soil properties, and fire determine the ecological
generate biological productivity and habitats for plant character of wet flats. Mineral-soil flats exhibit an
and animal biodiversity. Economically, forested wet- inverse hydroperiod–fire frequency continuum from
lands provide an important timber resource, and drier pine savannas to wet evergreen bay forests or
seasonally dry herbaceous wetlands can be grazed. deciduous hardwood swamps. Nutrient pulses from fires
However, wetland types differ in some ecosystem are rapidly resequestered in recovering vegetation. In
functions and services because of differences in land- areas of prolonged saturation or shallow flooding, peat
scape position, water sources, and hydrodynamics accretion results in organic-soil flats with evergreen
(Brinson 1993), as summarized from pertinent reviews shrub–bog (pocosin) vegetation that burns infrequently.
cited in the following paragraphs. Large expanses of pocosin, as on the North Carolina
Riverine wetlands vary from narrow riparian corri- Coastal Flats, sequester carbon in organic soils and
dors along small streams to large river floodplains with function in maintaining land surface (peat accretion) in
complex microtopography. These wetlands typically response to sea level rise. Wetland flats generally support
receive water as inflows from adjacent uplands or by fauna requiring interspersed terrestrial and wet habitats,
periodic overbank flooding. Seasonal flooding dynamics or fire-maintained vegetation (from Richardson and
influence substrates, biotic communities, and wetland Gibbons 1993, Harms et al. 1998, Rheinhardt et al.
functions. Floodplain wetlands function uniquely in 2002).
detaining high-energy floodwaters, attenuating peak Depressional wetlands include large Carolina bays
flows, and maintaining channel base flows. As part of and smaller wetlands (e.g., Delmarva bays, Citronelle
a landscape drainage network intercepting sediments, ponds, cypress domes) that are especially numerous
nutrients, and other pollutants, riverine and riparian across the Rolling Coastal Plain and some parts of the
wetlands also play a critical role in regulating the quality Coastal Flats. Found in various topographic positions,
of regional surface waters. Nutrients are retained and they develop in hollows with a subsurface confining
cycled internally, lost in gaseous forms through denitri- layer that promotes surface water ponding to depths of
fication (for nitrogen), and incorporated into organic 1 meter. Outlets may occasionally be present, but
materials for downstream export to detritus-based water levels mainly fluctuate vertically with seasonal and
estuarine food webs. Riverine wetland soils have more annual changes in rainfall and ET. Some groundwater
organic matter than upland soils; nutrient and sediment exchanges may occur, depending upon topographic
inputs contribute to high biological productivity where position, underlying substrates, and seasonal shifts in
soils are periodically aerated. Physiography influences ET and subsurface fluxes. Water storage may be small
wetland properties, as Piedmont-origin (red- or brown- on a unit basis, but the cumulative effect of many
water) rivers have more inorganic nutrients and depressions may be substantial at a watershed scale
sediment loads than Coastal Plain-origin (blackwater) (Brown and Sullivan 1988). In addition to storing
rivers that are nutrient-dilute but high in organic acids. rainwater, depressions may retain added nutrients if
Riverine wetlands are largely forested systems, with they receive water inflows and have limited outflows.
diverse forest types shaped by local interactions between Depending on size and location, depressional wetlands
hydrology and microtopography. Biological productiv- exhibit hydroperiod diversity from semipermanently
ity, structural complexity, and adjacency to uplands ponded to frequently dry; soil organic content and fire
make riverine wetlands some of the most ecologically susceptibility vary accordingly. These properties shape
and economically valuable wildlife and fisheries habitats plant communities that range structurally from open-
in the United States (from Sharitz and Mitsch 1993, water ponds to emergent marshes and swamp forests;
Hodges 1998, Kellison et al. 1998). hydroperiod and vegetation diversity in turn shape the
Wetland flats are common on coastal terraces where faunal communities. Because periodic drying restricts
low land relief and shallow subsurface confining layers the presence of permanent fish populations, depressional
result in saturated soils with poor lateral and vertical wetlands have a distinctive habitat function as breeding
drainage. Seasonal changes in evapotranspiration (ET) refugia for many aquatic invertebrates and amphibians
result in large water table fluctuations, which provide (from Richardson and Gibbons 1993, Sharitz 2003, De
rainwater storage after dry periods and release water Steven and Toner 2004).
slowly from saturated soils by diffuse flow to headwater
ETLAND IMPACTS FROM PIEDMONT–COASTAL
streams or other shorelines. Adjacent to coastal areas, W
such freshwater releases are important for regulating PLAIN AGRICULTURE
salinity conditions in estuarine habitats. Because flats The dominant regional soils are highly weathered
are mainly rain-fed and do not receive upland inflows, acidic and sandy Ultisols, with better-drained Udults on
they tend to be nutrient-limited, although this varies the Piedmont and Rolling Coastal Plain, and poorly
S6 DIANEDESTEVENANDRICHARDLOWRANCE Ecological Applications
Special Issue
drained Aquults on the Coastal Flats. Soils of the unclear what proportion was historical loss vs. acceler-
geologically younger Florida peninsula are mainly sandy ated loss in the mid-20th century from intensified
Entisols or poorly drained Spodosols (Aquods) (Foth agriculture. Apart from some localized areas with large
and Schafer 1980). Thus, natural soil infertility or soil conversions, proportionally less wetland area was
wetness have strongly influenced agricultural land use, drained in the Piedmont–Coastal Plain region compared
particularly after European settlement. For over 200 to the Upper Midwest and Lower Mississippi Valley
years, farming generally took the form of extensive (where proportional losses often exceeded 70%; Dahl
shifting cultivation. Forestland was cleared, cropped for 1990). Reflecting the dominant land use, managed
several years, then abandoned to open-range grazing timber harvest from forested wetlands is also a major
and forest regrowth while other land was cleared (or re- activity across the Coastal Plain (Kellison and Young
cleared) for new crops (Otto 1994). Colonists first settled 1997).
along fertile river valleys of the Coastal Flats, and Because Piedmont–Coastal Plain wetlands comprise
lowland wetlands were drained and cleared where high proportions of national wetland area, recent
possible (Lilly 1981, Dahl and Allord 1996). However, nationwide changes have tended to reflect regional
the land area needed for shifting agriculture prompted trends (Table 1). Annual rates of net wetland loss have
large population migrations inland to the better drained declined substantially since the mid-1950s. Agriculture
Rolling Coastal Plain and Piedmont. An extensive was the main cause of wetland loss until the mid-1980s,
agriculture of profitable cash and food crops (cotton, with high regional losses in the bottomland forests of the
tobacco, rice, corn) dominated until the economic Lower Mississippi Valley, the wet flats of coastal North
upheavals of the Civil War period, after which federal Carolina, and the freshwater marshes of the Everglades
drainage incentives and mechanized technologies began (Frayer et al. 1983, Hefner and Brown 1985). However,
shifting agricultural production farther westward by 2004, urban and rural development was the major
(Rasmussen 1960, Otto 1994). Following widespread cause of wetland loss (Dahl 2006). Declining rates of net
farmland abandonment during the economic depression loss have been attributed to the introduction of wetland
of the 1930s, much of the retired land reverted to natural regulation in the mid-1980s; this began a shift from
woodlandoractiveplantationforestry(Allenet al. 1996, unregulated impacts to either regulated and permitted
Carmichael 1997). losses under Clean Water Act Section 404 (on nonag-
Adiversified agriculture currently comprises ;20% of ricultural lands), or to disincentives against wetland
regional land area; concentrated livestock-feeding oper- drainage under Farm Bill Swampbuster provisions
ations are also common. On highly erodible Piedmont (on agricultural lands). Gains from wetland mitigation
soils, poor historic farming practices resulted in severe and restoration have also offset ongoing losses (Dahl
topsoil loss and gully erosion into waterways; conse- 2006). Another notable trend is a sustained increase in
quently, federal soil conservation programs promoted a freshwater ponds (open-water areas ,8 ha in size), with
land use shift to pine silviculture (Allen et al. 1996). The the result that the latest inventory recorded a net
Rolling Coastal Plain and Coastal Flats (where drainage wetland gain even as loss of vegetated wetlands
allows) remain a mix of pine forestry and agriculture. continues (Table 1). Half or more of the increase
Pastureland is concentrated in the Piedmont and Rolling represented created ponds on agricultural or developed
Coastal Plain, whereas the open flatwoods of south- lands (Dahl 2000, 2006). New ponds in the Southeast
central Florida support the only substantial rangeland- comprised a rising proportion of nationwide increases,
based grazing east of the Mississippi River. The more from 27% to 54% between the 1950s and 1990s (Table
populated mid-Atlantic states of the Chesapeake Bay 1); qualitative data (Dahl 2006) suggest that this trend is
watershed are more urbanized; however, a recent trend continuing.
is rapid urbanization across the Piedmont and in coastal
ETLAND CONSERVATION PRACTICES IN THE
areas at the expense of both agricultural and forestland, W
and at rates higher than national averages (Wear 2002, PIEDMONT–COASTAL PLAIN
USDANRCS2009). Under Farm Bill programs, conservation practices
Agricultural use of Piedmont and Rolling Coastal are applied to reduce soil erosion, protect water quality,
Plain uplands requires minimal artificial drainage, thus, and provide wildlife habitat or other environmental
impacts to adjacent wetlands typically involve upland benefits on agricultural lands. Among numerous prac-
runoffs or marginal drainage to accommodate field tices with defined implementation standards, those most
expansion. However, where landscape or wetland related to wetland ecosystem services are wetland and
internal drainage is poor (as on the Coastal Flats, or conservation buffer practices. Wetland practices
in wet flats or depressions generally), agriculture often involve restoring, creating, or managing wetland habi-
resulted in larger direct wetland losses because artificial tats. Pond construction may also be a wetland practice if
drainage is needed to bring lands into production. For it creates habitat meeting wetland definitions or is
the 200 years between the 1780s and 1980s, estimated designed to support wetland vegetation and fauna.
losses of original wetland area range from 25% to 55% Buffer practices are planted or protected vegetated areas
for most states of the region (Dahl 1990). However, it is designed to reduce upland impacts on adjacent wetland
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